Color-forming duplicating method

ABSTRACT

Hectograph duplication is carried out by bringing a master sheet carrying a predetermined pattern of images which is formed with an image-forming material consisting essentially of a colorless color forming compound selected from N-bis(p&#39;&#39;dimethylaminophenyl)methyl-m-hydroxymethyl-aniline and N-bis(p&#39;&#39;dimethylaminophenyl)methyl-p- Beta -hydroxyethyl aniline and a vehicle into contact with a copying sheet coated with a reactive solid material effective for developing the colorless color forming compound after wetting the coated surface of the copying sheet with a volatile neutral organic liquid capable of dissolving the colorless color forming compound but not capable of adversely effecting the reactivity of the reactive solid material, and developing the colorless color forming compound transferred onto the coated surface of the copying sheet so as to produce violet blue images.

[451 Nov. 27, 1973 Miyazawa et al.

[ COLOR-FORMING DUPLIC ATING METHOD 7 [75 Inventors: Yoshihide Miyazawa; Minoru Ozutslemi, both of Tokyo, Japan [73] ,Assignee: Hodogaya Chemical Co., Ltd.,

Tokyo, Japan [22] Filed: May 15, 1972 [21] Appl. No.: 253,472

[30] Foreign Application Priority Data May 20, 1971 Japan 46/33578 Apr. 28, 1972 Japan 47/42183 [52] US. Cl 101/469, 117/362, 101/473 [51] Int. Cl B4lm 5/00 [58] Field of Search 101/469, 473, DIG. l;

[56] References Cited UNITED STATES PATENTS 2,755,202 7/1956 Balon et al 1l7/36.2 2,755,420 7/1956 L0cke.... l17/36.2 5/1961 Kranz 117/36.2

3,034,917 5/1962 Francis et al. 117/362 Primary Examiner-David Klein Attorney-Robert E. Burns et al.

[5 7 ABSTRACT Hectograph duplication is carried out by bringing a master sheet carrying a predetermined pattern of images which is formed with an image-forming material consisting essentially of a colorless color forming compound selected from N-bis(p'- dimethylaminophenyl)methyl-m-hydroxymethylaniline and N-bis(p'-dimethylaminophenyl)methyl-p- B-hydroxyethyl aniline and a vehicle into contact with a copying sheet coated with a reactive solid material effective for developing the colorless color forming compound after wetting the coated surface of the copying sheet with a volatile neutral organic liquid capable of dissolving the colorless color forming compound but not capable of adversely effecting the reactivity of the reactive solid material, and developing the colorless color forming compound transferred onto the coated surface of the copying sheet so as to produce violet blue images.

6 Claims, No Drawings COLOR-FORMING DUPLICATING METHOD The present invention relates to a hectograph duplicating method, more particularly relates to a hectograph duplicating method wherein colorless images formed on the surface of an image master sheet are transferred onto a surface of a copying sheet and at the same time, developed into visible color images thereon.

The hectograph duplicating method is a practical duplicating method and recently, utilized broadly because of the following advantages:

1. easy production of image master sheet,

2. easy operation in duplicating,

3. high utility of the master sheet, for example, only one master sheet need be used for quickly duplicating about 100 to 500 copies and 4. low unit cost of duplicating.

In the conventional hectograph duplicating method, a duplicating fluid which mainly consists of volatile alcohol is used for transferring the images from the master sheet onto the copying sheet, and, such method is called the alcohol hectograph duplicating method. In this method, the duplication is carried out in the following way. That is, a duplicating ink containing one or more dyes soluble in volatile alcohol is applied to the surface of a substrate such as paper or film in order to provide a transfer sheet, and the transfer sheet surface which carries the duplicating ink thereon is brought into close contact with the dry surface of the paper sheet, and pressed in accordance with the pattern of the desired images by hand writing or typewriting, etc., so as to transfer the images formed on the transfer sheet to the paper sheet by pressing whereby an image master sheet is obtained.

After wetting the surface of a copying sheet such as paper or film with a duplicating fluid such as methyl alcohol and ethyl alcohol, the master sheet surface carrying the color images thereon is brought into contact with the wet surface of the copying sheet before the duplicating fluid evaporates away. By this contact, the dye in the color images on the master sheet surface is transferred onto the wet surface of the copying sheet, and at the same time, the dye is dissolved into the duplicating fluid so as to produce color images thereon. By repeating the above-mentioned operation, numerous-duplications can be effected from only one master sheet onto numerous copying sheets.

The color dyes usable for the conventional hectograph duplicating system are selected in consideration of duplicating ink characteristics such as dissolving property and dissolving rate in the duplicating fluid, desired hue and color depth of the duplicated images, compatibility with the vehicle used for producing the duplicating ink and workability in the production of the duplicating ink. Generally, the color dyes for the conventional hectograph duplicating system sre selected from triaryl methane dyes, for example, Methyl Violet, Ethyl Violet, Crystal Violet, Victoria Blue, Malachite Green and Rose Aniline. Practically, the color dyes are used in an amount of 50 to 200 percent based on the weight of the vehicle.

The duplicating fluid which is applied to the copying sheet in order to dissolve the dye in the duplicating ink is selected in consideration of dissolving property and dissolving rate of the dye used, wetting property for the copying sheet, volatile property at room temperature and penetrating property into the vehicle. The practical ydiethyl ether, acetone, 1,4-dioxane, benzyl alcohol, or

mixtures of two or more of the abovementioned liquids. The vehicle usable for producing the duplicating ink may be selected from vegetable, animal or synthetic waxes, for example, carnauba wax, montan wax and paraffin wax; mixtures of two or more waxes as mentioned above; and waxy mixtures consisting of major parts of one or more of the above-mentioned waxes and minor parts of one or more selected from higher fatty acids and higher fatty acid esters, for example, oleic acid and butyl stearate; alcohols such as ethylene glycol, glycerin and cetyl alcohol; and mineral oils.

The conventional hectograph duplicating method has I the above-stated advantages, but has the following disadvantages.

1. When the color dye is mixed with the waxy vehicle while heating in preparation of the duplicating ink, the color dye frequently tends to disperse away in atmosphere and this results in local soiling. 2. Since the color dye usable for the duplicating ink is easily soluble in alcohols and water, it frequently tends to soil the hands, clothes and copying machine during handling or preparing the transfer sheet and master sheet or during the duplicating operation.

3. The color dye can not be eliminated by washing with soap or synthetic detergents.

4. lf the master sheet carrying the color images is handled with hands soiled by the color dye and forms soil images on the master sheet surface, it results in undesirable duplication of the soil image onto the copying sheet.

Further, the color images duplicated onto the copying sheet by the above-stated conventional method have insufficient light fastness and water resistant property. Therefore, frequently difficulty in reading the duplicated images results.

in order to eliminate the above-stated disadvantages, a leuco Aurarnine compound of bis(p-substituted aminoaryl)-methane which is essentially colorless, is used as a duplicating color, namely, an image forming component, instead of the color dye used in the conventional method.

However, the leuco Auramine compounds in colorless or lightly colored powder form are unstable in atmosphere and tend to decompose and discolor when they are exposed to light, oxygen and water.

Also, in the case where the leuco Auramine compounds are mixed with a vehicle containing the abovementioned vegetable, animal or synthetic waxes, ethyl cellulose, polyvinyl acetate, polyvinyl chloride, styrene-isoprene copolymers, polyvinyl butyral resin, rosin modified alkyd resin, or mixtures of two or more of the above-mentioned members, the leuco Auramine compounds frequently decompose and develop into light blue or green by the action of the acidic property of the vehicle itself or impurities therein.

In order to prevent the leuco Auramine compounds from undesirable color development, an organic or inorganic basic compound, for example, sodium carbonate, sodium hydrogen-carbonate, 2,2',2"-trihydroxyethylamine, hydroxybenzyl-trimethyl ammonium salt and stearyl amine is added, as an anti-developing agent, into the duplicating ink in an amount of 5 to 20 percent based on the weight of the vehicle. However, the addition of the basic anti-developing agent results in decrease of solubility or compatibility of the leuco Auramine compounds in the vehicle and workability.

Furthermore, when the duplicating ink is applied on to the surface of a substrate such as paper or film and dried in order to prepare a transfer sheet, the addition of the antideveloping agent results in formation of cracked or uneven thick coating of the duplicating ink on the substrate.

Furthermore, when the transfer sheet thus prepared and having a lightly colored or colorless coating is exposed to the atmosphere for several days, or when the transfer sheet is contained in a closed glass container and exposed directly to sun light for several days, the leuco Auramine compound decomposes and becomes discolored brown to dark brown. As a result, the development of the duplicating ink transferred onto the copying sheet is obstructed, and sometimes the development is not quite effected.

In the conventional duplicating method using the leuco Auramine compound, a coated surface of the transfer sheet having a colorless or lightly colored coating is brought into close contact with a substrate such as paper or film to be made into a master sheet, and the coating on the transfer sheet is transferred onto the substrate by pressure of hand writing or typewriting, etc., in accordance with a pattern of predetermined images.

The copying sheet is prepared by coating the surface of a substrate such as paper or film with a dispersion of an active acid clay material such as acid clay, attapulgite, zeolite and bentonite; an organic solid acid such as succinic acid, maleic acid, tannic acid and benzoic acid; acid polymers such as phenol-aldehyde condensates, carboxypolyethylenes and styrene-maleic acid anhydride copolymers having a carboxylic acid group] or mixtures of two or more members as stated above, and then drying the coating. The copy sheet thus prepared is a so-called bottom sheet of pressure sensitive copying paper. In the copying operation, the coated surface of the copying sheet is wetted with a commercial spirit hectocarbon duplicating fluid consisting of major parts of volatile alcohol, for example, methyl alcohol, ethyl alcohol and iso-propyl alcohol and minor parts of B-hydroxydiethyl ether or benzyl alcohol but not containing acid substance, the wet surface of the copying sheet is brought into contact with the image canying surface of the master sheet and pressed thereto. By these operations, the leuco Auramine compound in the images of the master sheet is transferred onto the copying'sheet surface and dissolved into the duplicating fluid on the copying sheet before the duplicating fluid evaporates away. The dissolved compound is decomposed by the action of the active acid clay material so as to color develop on the copying sheet surface. However, the duplicating method utilizing the leuco Auramine compound has the following disadvanguishable with the naked eye, the surface of a thin copying sheet which has been used as a bottom sheet of duplicating paper is wetted with a spirit hectocarbon duplicating fluid consisting of a volatile alcohol and an acid substance such as salycilic acid, acetic acid and hydrochloric acid or an oxidizing agent such as tetrachloro-p-benzoquinone, the wet surface of the copying sheet is brought into contact with the image carrying surface of the master sheet and then pressed so as to transfer the images on the master sheet to the wet surface of the copying sheet. Upon comparing this modified method with the first method referred to the color developing rate of the transferred images is higher and the color depth of the developed color is somewhat higher. However, the modified method has the disadvantages that the metal parts of the copy machine contacting the copying sheet is corroded by the acid substance or oxidizing agent contained in he duplicating fluid applied onto the copying sheet, and when the resultant copies are fastened with a clip or the needle of a paper fastener and stored for a long time, the clip or needle becomes corroded by the acid substance or oxidizing agent remaining on the copies.

In one other modified duplicating method, the bottom sheet of the conventional pressure sensitive copying paper is used as the copying sheet, the surface of this copying sheet is wetted with an aromatic solvent such as benzene and toluene which has a high dissolving property for the leuco Auramine compound, and then the wet surface of the copying sheet is brought into contact with the image carrying surface of the master sheet and pressed so as to transfer the images on the master sheet to the wet surface of the copying sheet. This modified method is superior in that the transferred leuco Auramine compound is quickly developed into deep color. However, in this modified method, there are the disadvantages that the vapor of aromatic solvent such as benzene and toluene are prejudicial to the health of humans. Additionally, since in copying, the leuco Auramine compound in the images of the master sheet is dissolved in the duplicating fluid on the copying sheet surface in a greater amount than necessary and enough to form color images clearly distinguishable with the naked eye, the leuco Auramine compound on the master sheet is quickly consumed and therefore, one master sheet can produce a mere 50 copies or less.

An object of the present invention is to provide a method of hectographically duplicating images by transferring colorless image from the master sheet onto a copying sheet and developing the transferred colorless image into deep and clear color images having high light fastness, water-resistant property and resistance to chemicals.

As result of the inventors study for the purpose of removing the above-mentioned disadvantages of the conventional hectograph duplicating methods, the object of the present invention is accomplished by utilizing essentially colorless color forming compounds of the formula:

H3C\ /CH1 HaC IIIH CIh (CHQHOII wherein n is l or 2, and the group (Cl-l ),,OH of the anihydroxyethylaniline, have high stability even after exposure to atmosphere for several weeks or to sun light for several days, and the developed color from these color forming compounds has excellent water and weather-resistant properties, light fastness and resistance to chemicals. Such advantages of the method of the present invention can not be suggested from the already-known features of the leuco Auramine compound of bis(p-substituted aminoaryl) methanes which are also essentially colorless color forming compound.

' The N-bis(p-dimethylaminophenyl)methyl-mhydroxymethylaniline or N-bis(p'- dimethylaminophenyl)methyl-p-Bhydroxy-ethylaniline is admixed with a vehicle which, if necessary, containing, as anti-developing agent, an organic or inorganic basic compound, for example, sodium carbonate, sodium bicarbonate, calcium hydroxide, 2,2',2"-trihydroxyethylamine, pyridine and morpholine, in order to prepare a substantially colorless image-forming material, that is, a duplicating ink. The duplicating ink as state above can be easily applied onto the surface of a substrate such as paper and sheet to prepare a transfer sheet having a uniform thick coating with no cracks. Further, even after the transfer sheet is exposed to atmosphere for several weeks, or is contained in a closed glass container and exposed directly to sun light for several days, the coating is merely discolored slightly yellow and the color development potential of the color forming compound in the coating and function of the transfer sheet are not lowered.

In the method of the present invention, the predetermined pattern of colorless images are formed on the image master sheet in the process in which the coated surface of the transfer sheet is brought into contact with the surface of the master sheet and pressed on the face surface of the master sheet by pressure of hand writing, typewriting, etc., in accordance with a predetermined image pattern so as to transfer the colorless coating from the transfer sheet surface onto the master sheet surface in the predetermined pattern of the image. In order to effect the duplicating, the image carrying surface of the master sheet is brought into contact with the surface of a bottom sheet of commercial pressure sensitive paper, that is, copying sheet, wetted with a commercial spirit hectocarbon duplicating fluid containing mainly a volatile alcohol and no acid substance, and then pressed lightly. By this contact and pressure, the colorless color forming compound in the colorless images is transferred onto the surface of the copying sheet and dissolved into the duplicating fluid applied onto the copying sheet surface, and developed completely to deep clear violet blue almost instantly. Therefore, deep clear violet blue images are formed on the copying sheet. By repeating the abovementioned operations, numerous copies can be produced from only one master sheet. The color images thus produced on the copying sheet have high waterand weatherresistant properties, light fastness to radiation of a fluorescent lamp located just in front of the copying sheet and resistance to chemicals.

It should be noted that the above-stated excellent features of the copies produced by the method of the present invention can not be anticipated from the conventional methods in which the leuco Auramine compounds of bis(p-substituted aminoaryl)methane are used. Further, it should be noted that neither N-bis(p'- dimethylaminophenyl)methyl-o(or p)- hydroxymethylaniline nor N-bis(p'-dimethylaminophenyl)methyl-o(or m)-B-hydroxyethylaniline which are isomers of the colorless coloring matter usable for the method of the present invention, can import an effect similar to the colorless coloring compound of the present invention to the hectograph. if the abovementioned compounds are utilized instead of the N- bis(p'-dimethylaminophenyl)methylmhydroxymethylani line or N-bis(pdimethylaminophenyl )methyl-p-B-hydroxyethylaniline in order to prepare the duplicating ink, the resultant transfer sheet is discolored brown and its color development potential is lowered by exposure to atmosphere for a few days only. Further, in the above case, it is observed that if the fresh transfer sheet is used for the preparation of the master sheet, and immediately, the master sheet is subjecting to duplicating, the transferred potential images are developed into deep violet blue images on the copying sheet surface within one second, but the color images thus developed are discolored dark greenish blue within a few hours. These are the disadvantages of the N-bis(p-dimethylaminophenyl)methyl-o(or p)-hydroxymethylaniline and N- bis(p'-dimethylaminophenyl)methyl-o(or m)-]3- hydroxyethylaniline which distinguish them from the colorless color forming compound usable for the present invention.

The N-bis( p-dimethylaminophenyl )methyl-mhydroxymethylaniline or N-bis(p'- dimethylaminophenyl)methyl-p-B-hydroxyethylaniline which is usable for the method of the present invention can be prepared in the following process in a high yield and a high purity. 10 mol of p,pbis(dimethylamino)-benzhydrol and 0.7 to 1.2 mol, preferably, 0.9 to 1.0 mol of m-aminobenzyl alcohol or B-(p-arninophenyhethyl alcohol are dissolved into 400 to 800 ml of to 99 percent aqueous ethyl alcohol or 500 to 1,200 ml of a volatile organic inert solvent, for example, benzene, toluene, xylene and chlorobenzene, containing if necessary, boric acid anhydride. The reaction solution is refluxed for 2 to 9 hours, thereafter, cooled to a temperature of 0 to 20 C or distilled so as to evaporate the solvent in the reaction solution out of thereaction system, or poured into water. The resultant solid product is separated by filtering and is then washed and dried. If necessary, the dried product is recrystallized from a volatile organic solvent.

The method of the preparation of the colorless color forming compounds usable for the method of the present invention will be explained by the following illustration.

Preparation of N-bis(p'- dimethylaminophenyl)methyl-m-hydroxymethylaniline A reaction solution is prepared by dissolving 27 g of p,p'-bis(dimethylamino)benzhydrol and 12.3 g of maminobenzyl alcohol in 70 ml of 95 percent aqueous ethyl alcohol. The reaction solution is refluxed at a temperature of 80 to 85 C for 6 hours in order to react the above compounds with each other, and cooled to room temperature. The resultant precipitate is filtered; rinsed with 10 ml of aqueous ethyl alcohol and then dried. Colorless columner crystalline N- bis(p-dimethylaminophenyl)methyl-mhydroxymethylaniline having a melting point of 125 to 129 C are obtained in an amount of 30.3 g. The resultant crystals are recrystallized from benzene-n-hexane. The resultant crystals have a melting point of 133 to 135 C.

Even after the purified crystals are exposed to atmosphere for several weeks, no color development is observed thereon. When a solution of the crystals in methyl alcohol is applied onto the copying surface of a bottom sheet of commercial pressure sensitive copying paper, the surface of the bottom sheet is colored deep violet blue almost instantly.

Preparation of N-bis(pdimethylaminophenyl)methyl-m-hydroxymethylaniline A reaction solution is prepared by dissolving 27 g of p,p'-bis(dimethylamino)benzhydrol and 11.5 g of maminobenzyl alcohol in 700 ml of toluene. The reaction solution is refluxed at a temperature of 110 to 120 C for 2 hours while distilling produced water out of the reaction system together with toluene, and then cooled. The resultant precipitate is separated by filtering and rinsed with 20 ml of alcohol-water. The product is 28.4 g of light yellow columner crystalline N-bis(p'- dimethylaminophenyl)methyl-m-hydroxymethylaniline having a melting point of 129 133 C.

When a solution of the crystals in ethyl alcohol is applied onto the surface of a bottom sheet of pressure sensitive copying paper, the surface of the bottom sheet is colored deep violet blue almost instantly.

Preparation of N-bis(pdimethylaminophenyl)methyl-p-fi-hydroxyethylaniline A reaction solution is prepared by dissolving 27 g of p,p-bis(dimethylamino)benzhydrol and g of B-(paminophenyl)-ethyl alcohol in 100 g of 99 percent ethyl alcohol. The reaction solution is refluxed at a temperature of 80 C for 10 hours and then cooled to 0 C. The precipitated crystals are separated by filtering, rinsed with g of 99 percent cold ethyl alcohol and dried under reduced pressure. The product is 32 g of light yellow crystalline N-bis(p'- dimethylaminophenyl)methyl-p-B-hydroxyethylaniline having a melting point of 122 to 125 C. The crystals are recrystallized from toluene. The resultant colorless crystals have a melting point of 130 to 131 C.

From observation of the infrared absorption spectrum of the crystals, it is observed that there are specific absorption bands of v and m When the solutions of the crystals in methyl alcohol or toluene are absorbed by acid clay, the surface of the acid clay is immediately colored violet blue.

Preparation of N-bis(p'- dimethylaminophenyl)methyl-p-B-hydroxyethylaniline A solution of 27 g of p,p'-bis(dimethylamino)benzhydro] and 15 g of fl-(p-aminophenyDethyl alcohol in 600 ml of xylene is refluxed at a temperature of to 130 C for 2 hours while distillating produced water out of the reaction system. The reaction solution is cooled and the resultant solid product is separated by filtering and is then rinsed with 20 ml of water-ethyl alcohol mixture. Yellow crystalline N-bis(pdimethylaminophenyl)methyl-p-fi hydroxyethylaniline with a melting point of 121 to C is obtained in an amount of 30 g. The crystals are dissolved in ethyl alcohol. When the solution is absorbed on the coated surface of a bottom sheet of pressure sensitive copying paper, the surface of the bottom sheet is perfectly colored deep violet blue almost instantly.

In order to carrying out the method of the present invention, a duplicating ink is prepared using N-bis(pdimethylaminophenyl)methyl-m-hydroxymethylaniline or hydroxyethylaniline, a transfer sheet is prepared using the above-stated duplicating ink, and thereafter, a master sheet is prepared using the transfer sheet by transferring the duplicating ink coated on the transfer sheet onto the surface of the master sheet in accordance with a predetermined pattern of images.

In duplicating, the image carrying surface of the master sheet is brought into contact with the coated surface of the copying sheet such as a bottom sheet of pressure sensitive copying paper after the coated surface is wetted with a commercial spirit hectocarbon duplicating fluid mainly containing volatile alcohol but not containing acid substance, and then they are pressed lightly to each other. By the above operations, the colorless color forming compound contained in the colorless images on the master sheet is transferred onto the coated surface of the copying sheet and dissolved in the duplicating fluid on the coated surface. The dissolved colorless color forming compound is developed completely almost instantly so as to produce deep clear violet blue images on the coated surface of the copying sheet. By repeating the above operations, numerous copies can be produced from only one image master sheet.

The vehicle for the colorless color forming compound may consist of major parts of a member selected from carnauba wax, montax wax, paraffin wax, beeswax, ethyl cellulose, polyvinyl acetate, polyvinyl chloride, polyvinyl pyrrolidone, styrene-isobutylene co polymers, polyvinyl butyral resin, rosin modified alkyd resin or mixtures of two or more of the above-stated members and minor parts of a member selected from solid fatty alcohols such as cetyl alcohol, myristyl alcohol, and stearyl alcohol, solid glycol ethers such as polyethylene glycol ethers and polypropylene glycol ethers, animal oils, vegetable oils, mineral oils or mixtures of two or more of these members.

However, in consideration of the anti-developing property and workability of the colorless color forming compound during the processes of producing the duplicating ink and transfer sheet, stability of the transfer sheet over a long time storage and transferring and developing property of the colorless color forming matter in duplicating, it is desirable that the vehicle has a low acid value or contains an organic or inorganic basic compound, for example, sodium carbonate, sodium hydrogencarbonate, calcium hydroxide, 2,2',2"-trihy- 1 droxyethylamine, pyridine and morphorine, and that N-bis(p'-dimethylaminophenyl)methyl-p-B- formed on the master sheet during duplicating operations.

In order to satisfy the above-stated requirements, it is preferable that the vehicle consists of major parts of a member selected from ethyl cellulose, polyvinyl acetate, polyvinyl pyrrolidone, polyvinyl butyral resin, rosin modified alkyd resin and mixtures of two or more of above-mentioned members and minor parts of a member selected from solid fatty alcohols, animal oils, vegetable oils, mineral oils and mixture of two or more of the members mentioned above. More preferably the vehicle contains at most 2 percent of the organic or inorganic basic compound as stated hereinbefore based on the weight of the vehicle. Additionally, if it is necessary, the vehicle may include an amount of an antioxidant or ultraviolet ray absorber pertinent to the vehicle as a stabilizer.

The colorless color forming compound is dispersed in the vehicle as stated hereinbefore in an amount of 50 to 200, preferably, 110 to 160 percent based on the weight of the vehicle. The substrate for the duplicating ink may be selected from commercial papers and films, preferably, from commercial alkalline paper which is prepared by treating paper with alkali. In the preparation of the transfer sheet, it is desirable to apply the duplicating ink in an amount of 5 to 30 g, more preferably, to g of the colorless color forming matter per 1 m of the transfer sheet.

Since the images formed on the master sheet are colorless or slightly yellow, it is somewhat difficult to read, modify or correct the images. Therefore, a small amount of coloring compound such as a dye or pigment insoluble or barelysoluble in the duplicating fluid may be mixed into the duplicating ink or the vehicle or a solution or dispersion of the coloring compound may be applied onto the duplicating ink coating on the transfer sheet.

The duplicating fluid usable for the method of the present invention is a volatile organic liquid and must satisfy the following conditions.

1. The duplicating fluid must not lower or lower only very little the reaction activity of the acid substance in the coating on the copying sheet such as the bottom images on the master sheet, must dissolve the colorless color forming compound without premature developing in an amount necessary and sufficient to form clear and deep color images on the copying sheet, and must transfer the colorless color forming compound from the master sheet onto the copying sheet.

5. The duplicating fluid must not obstruct the almost instant development of the colorless color forming compound transferred from the master sheet into a deep clear violet blue.

6. After the formation of color images on the copying sheet, the duplicating fluid must evaporate away from the copying sheet immediately.

7. After the evaporation of the duplicating fluid, the surface of the copying sheet must not allow bleeding or repelling of oil ink from a ball point pen or a typewriter or aqueousink from a pen or fountain pen.

8. The duplicating fluid must not decrease the waterand weather-resistant properties, light fastness to, for example, radiation from a fluorescent lamp located just in front of the copying sheet, and resistance to chemicals, of the developed color images.

9, The duplicating fluid must not corrode the copying machine.

10. The duplicating fluid must be non-toxic and otherwise harmless and must have littleor no offensive or irritative odor.

The duplicating fluid usable for the method of the present invention and satisfying the above requirements may consist of major parts of methyl alcohol, ethyl alcohol or iso-p'ropyl alcohol and minor parts of fl-hydroxymethylethyl ether or B-hydroxydiethyl ether. That is, the commercial spirit hectocarbon duplicating fluid may be used as the duplicating fluid of the method of the present invention. if it is necessary, the duplicating fluid may contain a small amount of cationic or non-ionic surface active agent.

In order to developthe colorless color forming compound, a copying sheet such as the bottom sheet of commercial pressure sensitive copying paper carrying a reactive acid solid material thereon is used. The reactive acid solid material may be selected from active clay materials such as acid clay, attapulgite, zeolite and bentonite; organic solid acids such as succinic acid, maleic acid, tannic acid and benzoic acid; acid polymers such as phenol-aldehyde condensates, carboxypolyethylene and styrene-maleic acid anhydride copolymers having carboxylic acid group; or mixtures of two or more of these compounds.

Preferably, the reactive acid solid material is selected from the active clay materials and mixtures of the active clay material and the above-mentioned polymer. If necessary, a solid oxidizing agent such as ferric chloride and tetrachloro-p-benzoquinone may be applied together with the acid solid material onto the copying sheet. The acid solid material may be applied onto the copying sheet in an amount of 5 to 30 g preferably, 10 to l5 g per 1 m of the copying sheet.

The present invention will be further illustrated by the following examples which are given by way of illustration and not as limitation on the scope of the present invention.

EXAMPLE 1 A dispersion was prepared by homogenizing 21 g of rosin modified alkyd resin, 18 g of polyvinyl acetate, 3 g of beeswax, 2 g of motor oil, 55 g of N-bis(p'-- dimethylaminophenyl) methyl-mhydroxymethylaniline, 50 g of iso-propyl alcohol, 0.5 g of calcium hydroxide and 0.4 g of 2,2',2"-trihydroxyethylamine at room temperature for one hour using a closed colloid mill.

The dispersion thus prepared was uniformly applied onto the surface of a piece of commercial alkaline paper treated with alkali so as to show non-acidic property, using a coating doctor blade in order to coat it with the dispersion at a uniform thickness and then, the coated paper was dried by blowing hot air onto the treated surface. The coating on the alkaline paper contained 10 g of N-bis(p-dimethylaminophenyl)methylm-hydroxymethylaniline per 1 m of the alkaline paper. The coated surface of the alkaline paper was further coated uniformly with a 20 percent solution of polyvinyl alcohol in methyl alcohol and then dried.

The doubly coated paper which was substantially colorless was cut to a desired size to prepare transfer sheets.

A fine quality paper was brought into contact with the coated surface of the transfer sheet and pressed thereon in accordance with the predetermined pattern of image so as to transfer the coating on the transfer sheet to the surface of the fine quality paper in the predetermined pattern of image. The transferred image on the fine quality paper were in a mirror image relationship to the original images. The fine quality paper thus image-transferred was used as an image master sheet.

Another dispersion was prepared by uniformly mixing 75 g of acid clay, 25 g of bentonite, 5 g of polyvinyl alcohol and 200 g of water at a room temperature for 3 hours. The dispersion was uniformly applied onto a surface of a fine quality paper using a coating doctor blade to coat it, and then dried by blowing hot air onto the coated surface.

The coating thus applied contained g of the sum of acid clay and bentonite per 1 m of the fine quality paper. The coated paper was cut to a predetermined size to prepared copying sheets.

A duplicating fluid was prepared by uniformly mixing 90 parts by weight of ethyl alcohol and 10 parts by weight of B-hydroxydiethyl ether.

The master sheet was mounted in a copying machine so as to bring the image carrying surface of the master paper into contact with the coated surface of the copying sheet.

The coated surface of the copying sheet was wetted with the duplicating fluid and the wet copying sheet was brought into contact with the image-carrying surface of the master sheet and then pressed under a small pressure. Then, the N-bis(pdimethylaminophenyl)methyl-m-hydroxymethylaniline contained in the images on the master sheet was transferred onto the copying sheet surface and dissolved into the duplicating fluid on the copying sheet surface, whereby deep and clear violet blue images were formed on the copying sheet surface almost instantly.

By repeating the above copying operations, 200 copies were obtained on which surfaces deep and clear violet blue images were formed using only one imagecarrying master sheet.

It was established that the violet blue images thus developed on the copying sheet surfaces had excellent water-and weather resistant properties, light fastness to radiation of a fluorescent lamp located just in front of the copying sheet and resistance to chemicals. After the images were transferred from the master sheet to the copying sheet, the wetness of the transfer liquid on the copying sheet quickly disappeared so as to obtain the dry condition. Under such condition, it was observed that when the copying sheet was written with a pen or ball point pen, the aqueous ink of the pen or oil ink of the ball point pen was successfully absorbed by the copying sheet without bleeding or repelling. On the other hand, the colorless images on the abovementioned master sheet did not color develop substantially, and thus the master sheet could be used again for copying even after storage for a long time. Also, even after the transfer sheet was exposed to atmosphere for several weeks, no color development was observed on the transfer sheet surface, and color developing potential of the coating on the transfer sheet did not decrease.

For comparison, a transfer dispersion was prepared using a colorless lenco Auramine compound of bis(psubstituted aminoaryl)methane selected from wellknown N-bis(p-dimethyl-aminophenyl)methyl-pmethoxyaniline, N-bis(p-dimethylaminophenyl)methyl-p-chloroaniline, N-bis(p'- dimethylaminophenyl)-methyl-octadecylamine, N- bis(p -dimethylaminophenyl)-methyl piperidine, and N-bis(p'-dimethylaminophenyl)methyl-N- methylpiperidine, instead of the dimethylaminophenyl)methyl-mhydroxymethylaniline, and thereafter a comparison transfer sheet was prepared using the comparison dispersion and a comparison master sheet was prepared from the comparison transfer sheet in the same procedure as the present example.

The same copying operations as in the present example were repeated using the comparison image master sheets and the same duplicating fluid and copying sheets as those of the present example. In these copies, light violet blue to green images were merely formed on the copying sheet surfaces after several tens of seconds, and even after exposing them to the atmosphere for about 10 minutes, deep clear images could not be produced on the copying sheet.

Upon exposing the transfer sheets to atmosphere for a few days, the coating on the transfer sheets was colored brown or dark brown and the color developing potential of the colorless compound remarkably decreased.

For further comparison, the same procedures as in the present example were repeated using colorless N- bis(p-dimethylaminophenyl)methyl-o (or p)- hydroxymethylaniline which is an isomer of the colorless color forming compound of the present example in order to prepare a comparison transfer sheet and image master sheet. The same copying operation as the present example was repeated using the comparison image master sheet and the same transfer liquid and copying sheet as those of the present example.

In these copies, deep violet blue images were fonned on the copying sheet immediately, but the images were discolored dark green blue after exposure to atmosphere for a few hours, and the clarity and contrast of the images decreased. Upon exposing the comparison transfer sheet to atmosphere for a few days, it was found that the coating on the transfer sheet was discolored yellow brown and the color developing potential of the colorless compound decreased.

EXAMPLE 2 A dispersion was prepared by uniformly dispersing 20 g of rosin modified alkyd resin, 20 g of ethyl cellulose, 5 g of motor oil, 54 g of N-bis(p'- dimethylaminophenyl)methyl-mhydroxymethylaniline, 0.5 g of sodium hydrogene carbonate and 0.4 g of morpholine in ml of ethyl alcohol. The dispersion thus prepared was uniformly applied onto the surface of a piece of alkaline paper in an amount of 10 g of the N-bis(p'- dimethylaminophenyl)methyl-m-hydroxymethylaniline per 1 m of the alkaline paper using a coating doctor blade so as to form a uniform coating thereon, and then the coated surface was dried by blowing hot air thereonto. The dried paper was cut to a desired size to prepare colorless transfer sheets. The transfer sheet was subjected to the preparation of the image master sheet by the same method as Example 1.

A reaction mixture of 60 g of p-phenylphenol, 40 g of p-phenyl salicylic acid, 50 g of an 35 percent aqueous solution of formaldehyde, 2 g of oxalic acid anhydride, ml of concentrated hydrochloric acid and 400 ml of water was refluxed for hours, and then the resultant aqueous phase was separated from the reaction mixture. The remainder was dried under reduced pressure. A resinous material was obtained. The resinous material was added into 3 litres of xylene and was uniformly applied onto the surface of a paper using a coating doctor blade in an amount of 15 g of the resinous material per 1 m of the paper so as to form a uniform coating on the paper surface. Next, the coated paper was dried by blowing hot air thereonto and cut to the desired size so as to prepare copying sheets. A uniform duplicating fluid was prepared by dissolving 10 parts by volume of fl-hydroxyethylmethyl ether and 90 parts by volume of methyl alcohol.

The uniform duplicating fluid was applied onto the coated surface of the copying sheet using a hand addresser to wet it, and the wet surface of the copying sheet was brought into contact with the image-carrying surface of the image master sheet and lightly pressed.

By this copying operation, the potential color images on the master paper were transferred onto the coated surface of the copying sheet and developed by the duplicating fluid almost instantly, and deep clear violet blue images were formed on the coated surface of the Copying sheet. The violet blue images thus developed had excellent water-and weather-resistant properties, light fastness under fluorescent lamp radiation and resistance to chemicals. Further, it was established that coated surfaces of copying sheets on which color images have been developed satisfactorily absorb aqueous and oil inks without bleeding or repelling in practice. Every image master sheet could be used for making 200 copies without trouble. All the copies had clear deep violet blue images thereon.

On the other hand, even after the transfer sheet was exposed to atmosphere for several weeks, practically no dis-coloration and no decrease of the color developing potential of the transfer sheet were observed.

For comparison, the same procedures as the present example were repeated using the same bis(p-subsituted amino-aryl)metha.nes as stated in Example 1 instead of N-bis(p'-dimethyl-aminophenyl)methyl-mhydroxymethylaniline useful for the present invention. This comparison procedure resulted merely in the formation of light violet blue or green images on the copying sheet after several tens of seconds, and the light images did not develop into deep clear images even after exposure to atmosphere for about 10 minutes. Upon exposing the transfer sheet to atmosphere for several days, the coating on the transfer sheet was discolored brown or dark brown and the color developing potential of the colorless color forming compound decreased.

For further comparison, the same procedures as in Example 1 were repeated using N-bis(p'- dimethylaminophenyl)methyl-o (or p)- hydroxymethylaniline which is an isomer of N-bis(pdimethylaminophenyl)methyl-mhydroxymethylaniline. In copying, deep clear violet blue images were produced on the copying sheet surface almost instantly but the images were discolored to EXAMPLE 3 A colloidal homogenizer was charged with 10 g of polyvinyl butyral resin, 15 g of rosin modified alkyd resin, l0 g of ethyl cellulose, 5 g of cetyl alcohol, 5 g of linseed oil, 0.3 g of polyethyleneglycol butyl ester, 0.2 g of calcium hydroxide 0.2 g of 2,2',2"-trihydroxyethylamine, 0.1 g of 2,6-di-tertiary butyl phenol, 60 g of N-bis(p'-dimethylaminophenyl)-methyl-mhydroxymethylaniline, 60 ml of isopropyl alcohol to prepare a dispersion for a transfer sheet, and the charged mixture was homogenized at room temperature for 2 hours. A transfer sheet was prepared by the same method as in Example 1 utilizing the above-prepared dispersion. Subsequently, image master sheets were prepared from this transfer sheet.

A mixture of 94 g of phenol, g of 35 percent formaldehyde solution in water, 1 g of oxalic acid anhy dride, 10 ml of concentrated hydrochloric acid and 500 ml of water was refluxed for 10 hours at the boiling point thereof and cooled to room temperature, and thereafter, the aqueous phase was separated from the reaction product, and the remainder which was a resinous lump was dried under reduced pressure.

The resultant resinous lump was dissolved in an amount of g into 3 litres of toluene. Acid clay was added to the solution in an amount of g so as to prepare a suspension. The suspension thus prepared was applied onto the surface of a piece of paper in an amount of 10 g of the resinous lump per 1 m of paper to form an even thick coating, and the applied coat was dried by blowing hot air thereonto. The dried paper was cut to a desired size to prepare copying sheets.

After the coated surface of the copying sheet was wetted by methyl alcohol which was applied by a hand addresser, the wet surface of the copying sheet was brought into contact with the image-carrying surface of the master sheet, and pressed lightly. Deep clear violet blue images which were perfectly developed from the colorless images on the master sheet were produced on the coated surface of the copying sheet almost instantly. The images thus produced had superior waterand weather-resistant properties, light fastness under radiation from a fluorescent lamp located just in front of the sheet, and resistance to chemicals. Also, itwas established that the coated surface of the copying sheet on which the color images have been produced satisfactorily absorbs aqueous and oil inks without bleeding or repelling. Every image master sheet can produce copies without trouble, and deep clear violet blue images can be obtained on every copying sheet surface.

On the other hand, even after the transfer sheet was exposed to atmosphere for several weeks, practically no discoloration of the coating on the transfer sheet or lowering of the color developing potential were observed.

For comparison, the same procedures as in Example l were repeated except that the known N-bis(p'- dimethylamino-phenyl)methyl-p-dodecylphenylaniline and N-bis(p-dimethyl-aminophenyl)methyl-pdodecylamine were used instead of the N-bis(pdimethylaminophenyl)methyl-mhydroxymethylaniline. By the above procedure, light violet blue images were merely produced on the copying sheet surface after several tens of seconds, and did not convert to deep images even after exposure to atmosphere for about ten minutes. Also, by exposing the transfer sheet to atmosphere for a few days, the coated surface thereof became brown and the color developing potential thereof was lowered.

EXAMPLE 4 A colored transfer ink was prepared by mixing 10 g of carnauba wax, g of bleached montan wax, 5 g of beeswax, 5 g of cetyl alcohol, 10 g of stearyl amine, l g of 2,2',2-tri-hydroxyethylamine, 0.5 g of calcium hydroxide, 53 g of N-bis(p'- dimethylaminophenyl)methyl-m-hydroxymethylaniline and 0.2 g of Monolite Fast Orange 3G (trade mark of a pigment made by ICI) in methyl alcohol, by way of a three member roll mill while heating it.

A colored transfer sheet was prepared by the same procedures as in Example 1 by utilizing the aboveprepared colored transfer ink followed by the preparation of an image master sheet therefrom.

The same copying sheet as in Example 3 was wetted by methyl alcohol by way of a hand addresser, and thereafter, the wet surface of the copying sheet was brought into contact with the image-carrying surface of the master sheet and pressed lightly. By the aboveoperatons, completely developed deep clear violet blue images were produced on the coated surface of the copying sheet almost instantly. It was established that the violet blue images in practice, had sufiiciently good water-and weather resistant properties, light fastness to radiation from a fluorescent lamp located just in front of the copying sheet and resistance to chemicals, and the coated surface of the copying sheet on which the color images have been produced, has an excellent anti-bleeding property to aqueous and oil inks applied thereonto.

Every master sheet can be used to produce 250 copies with deep clear violet blue images without trouble. Upon exposing the transfer sheet to atmosphere for a few weeks, no decrease of color developing potential was observed.

For comparison, the same procedures as in the present example was repeated using known N-bis(pdimethylaminophenyl )methylmorpholine, and N- bis[p-(di-B-hydroxyethylamino )phenyll-methyl-pmethoxyaniline instead of N-bis( p dimethylaminophenyl)methyl-mhydroxymethylaniline, to produce transfer sheets, and image master sheets were prepared from the transfer sheets.

The same copying sheet as in Example 1 was used to copy from the comparison master sheet as stated above. Light violet blue images were produced on the coated surface of the copying sheet after several tens of seconds, and they became blue after exposure to atmosphere for about ten minutes.

An image master sheet prepared from a transfer sheet which has been exposed to atmosphere for several days, has a lowered color developing potential in copying.

For further comparison, N-bis(p'-dimethylaminophenyl)methyl-o (or p)-hydroxymethylaniline which is an isomer of the colorless color fonning compound used in the present example, was utilized for preparing a transfer sheet and then an image master sheet was prepared from the transfer sheet.

The images on the master sheet were transferred to the same copying sheet as in Example 1 using the same methyl alcohol duplicating fluid as in Example 1.

By this transfer, perfectly developed deep clear violet blue images were immediately produced on the coated surface of the copying sheet. The images thus devel oped became dark greenish blue images after exposure for a few hours, and the clarity of the images disappeared and the contrast of the images lowered. The master sheet which has been prepared from a comparison transfer sheet as stated above, has a remarkably decreased color developing potential in copying after the exposure.

EXAMPLE 5 A semi-closed sand mill was charged with 20 g of rosin modified alkyd resin, 15 g of polyvinyl acetate, 3 g of beeswax, 2 g of motor oil, 60 g of N-bis(p'- dimethylaminophenyl)methyl-p-B- hydroxyethylaniline, and 30 g of iso-propyl alcohol, and homogenizes them at room temperature for 3 hours. The resultant uniform dispersion was applied onto a surface of a piece of alkaline paper which is a thin paper treated with an alkali so as to show non-acidic property, in an amount of 10 g of the above-mentioned N-bis(p'-dimethylaminophenyl)methyl-p-B- hydroxyethylaniline per l m of the alkaline paper by way of a coating doctor blade to coat the alkaline paper at a constant thickness. The coated paper was dried by blowing hot air thereonto and cut to a desired size. Substantially colorless transfer sheets were obtained. The transfer sheet was superposed on a piece of fine quality paper so as to cause the coated surface of the transfer sheet to make contact with the fine quality paper and pressed on the face surface of the fine quality paper in accordance with the predetermined pattern of the image so as to transfer the patterned images from the transfer sheet to the contacted surface of the fine quality paper in a mirror image relationship to the original image.

The fine quality paper on which the transferred images are carried was used as an image master sheet.

One other dispersion was prepared by uniformly dispersing g of acid clay, 25 g of bentonite, and 5 g of polyvinyl alcohol in 200 ml of water at room temperature for 3 hours. The resultant dispersion was applied onto the surface of a piece of fine quality paper in an amount of 15g of the sum of the acid clay and the bentonite per 1 rn of the paper by means of a coating doctor blade to form a colorless coating having a uniform thickness thereon. Next, the coated surface of the fine quality paper was dried by blowing hot air thereonto, and then the dried paper was cut to the predetermined size in order to prepare copying sheets.

A constant quality solution usable for duplicating fluid was prepared by dissolving 5 parts by volume of B-hydroxy-ethylmethyl ether in parts by volume of ethyl alchol.

The image master sheet and the copying sheet were mounted on a copying machine so as to bring the image-carrying surface of the master sheet into contact with the coated surface of the copying sheet, and the coated surface of the copying sheet was wetted by the duplicating fluid. When the wet surface of the copying sheet was brought into contact with the image carrying surface of the master sheet, the N-bis(p'- dimethylaminophenyl)methyl-p-B-hydroxyethylaniline contained in the colorless images on the master sheet was dissolved in the duplicating liquid on the copying sheet whereby the images on the master sheet were transferred onto the coated surface of the copying sheet and deep clear violet blue images were almost instantly produced thereon. By repeting the abovementioned copying operation, 200 copies were made from only one master sheet, and deep clear violet blue images were produced on every copying sheet.

The violet blue images thus produced on the copying sheet had excellent properties of light fastness, waterresistance and anti-bleeding to aqueous and oil inks.

Further, it was observed that the coated surface of the copying sheet on which the duplicating fluid has been applied before copying, was substantially dry just after the color images were produced thereon. At this time, it was also observed that oil ink from a ball point pen and aqueous ink from a pen were successfully absorbed by the dry coated surface of the copying sheet without bleeding or repelling.

On the other hand, the colorless images retained on the master sheet were not developed even after copying as stated above, and the master sheet was able to be used again for copying even after storage for a long time.

For comparison, the same procedure as the present example was repeated except that N-bis(pdimethylaminophenyl)methyl-o(or m)-[3- hydroxyethylaniline was used instead of the colorless color forming compound used in the present example. A comparison showed that the colorless image of the comparison master sheet was successfully developed into deep violet blue images on the samecopying sheet as that of the present example, but the color images thus produced discolored to dark greenish blue after exposing to atmosphere for a few hours.

What we claim is:

1. A hectograph duplicating method comprising 1. providing a master sheet the surface of which carries a predeterined pattern of images formed with an image forming material consisting essen-- tially of a colorless color forming compound of the formula:

18 HaC\ CH:

HaC IfH \CII3 (CIIQDOH wherein n is l or 2, and the group (CHQnOH in the aniline residue is in m-position when n is l or in p-position when n is 2, and a vehicle for the colorless color fonning compound,

2. bringing the image-carrying surface of the master sheet into contact with the surface of a copying sheet which surface is coated with an acid reactive solid material effective for developing the colorless color forming compound of the master sheet after wetting the coated surface of the copying sheet with a volatile neutral duplicating fluid consisting essentially of a volatile alcohol effective for dissolving the colorless color fonning compound of the master sheet without adversely effecting the reactivity of the reactive solid material of the copying sheet, and

3. pressing the master sheet to the copying sheet,

' whereby the colorless color forming compound is transferred onto the copying sheet surface and developed into a color image thereon.

2. A hectograph duplicating method as in claim 1, wherein the colorless color forming compound is N- bis(p'-dimethylaminophenyl)methyl-mhydroxymethylaniline.

3. A hectograph duplicating method as claimed in claim 1, wherein the colorless color forming compound is N-bis(p-dimethylaminophenyl)methyl-p-B- hydroxyethylaniline.

4. A hectograph duplicating method as claimed in claim 1, wheren the colorless color forming compound is in 2. amount of 50 to 200 percent based on the weight of the vehicle.

5. A hectograph duplicating method as claimed in claim 4, wherein the amount of the colorless color forming compound is .to percent based on the weight of the vehicle.

6. A hectograph duplicating method as claimed in claim 1, wherein the image-forming material of the master sheet further comprises at most 2 percent of an organic or inorganic basic compound based on the weight of the vehicle. 

2. A hectograph duplicating method as in claim 1, wherein the colorless color forming compound is N-bis(p''-dimethylaminophenyl)methyl-m-hydroxymethylaniline.
 2. bringing the image-carrying surface of the master sheet into contact with the surface of a copying sheet which surface is coated with an acid reactive solid material effective for developing the colorless color forming compound of the master sheet after wetting the coated surface of the copying sheet with a volatile neutral duplicating fluid consisting essentially of a volatile alcohol effective for dissolving the colorless color forming compound of the master sheet without adversely effecting the reactivity of the reactive solid material of the copying sheet, and
 3. A hectograph duplicating method as claimed in claim 1, wherein the colorless color foRming compound is N-bis(p''-dimethylaminophenyl)methyl-p- Beta -hydroxyethylaniline.
 3. pressing the master sheet to the copying sheet, whereby the colorless color forming compound is transferred onto the copying sheet surface and developed into a color image thereon.
 4. A hectograph duplicating method as claimed in claim 1, wheren the colorless color forming compound is in a amount of 50 to 200 percent based on the weight of the vehicle.
 5. A hectograph duplicating method as claimed in claim 4, wherein the amount of the colorless color forming compound is 110 to 160 percent based on the weight of the vehicle.
 6. A hectograph duplicating method as claimed in claim 1, wherein the image-forming material of the master sheet further comprises at most 2 percent of an organic or inorganic basic compound based on the weight of the vehicle. 